Differential fluid pressure control system



uMarch 23, 1937.' R. s. BoHANNAN 2,0743

DIFFERENTIAL FLUID/ PRESSURE CONTROL SYSTEM BY/W@ ATTORNEYS March 23, 1937 R. s. BOHANNAN L DIFFERENTIAL FLUID PRESSURE CONTROL SYSTEM Filed May a, 1955 s sheets-sheath sgg INVENTOR IZ. .o/zafn/nan/ BY g X l ATToRNEY March 2 3, 1937. R,- As, BOHANNAN 2,074318 DIFFERENTIAL FLUID PRESSURE CONTROL SYSTEM Filed May s, 1955 l sheets-sheet s INVENTOR ATTORNEYS rear wheel brakes.

Patented Mer. 2a, '1931 i UNITED STATES APATEN'I OFFICE .DIFFERENTIAL FLUID PRESSURE con'rno SYSTEM Robert s. Bahamian, Birmingham, an.

Application May 8, 1935, Serial No. 20,338 1s claims. (ci. lss-152) of'the variable leverage control either between the transmission from the pedal to the pressure generating pistons or between such pistons and the points of use by means of control plungers exposed to the pressure in the different pressure 5 lines at any convenient points therein, the latter arrangement making it possible to place the control wherever desired as on the dash of the auto- My invention relates to apparatus for the control of fluid pressure in various uses such, for

instance, as to apply with variable and differen- In the practical use of such brake applying mechanism, it has been found highly desirable that diiierent pressures be utilized on the front and rear brakes and that the control mechanism4 for applying the different' pressures should be capable of ready adjustment to make the de-4 sired division' of the total braking pressure de veloped by the pedal. Such an arrangement contemplates, for instance, that the front brakes may receive 40% .of the total developed vpressure 2 and the rear brakes 60%. It is important, and

in tact essential for the best results, that this percentage should remain a `constant throughout the full range of the braking pressure developed by the pedal, and to obtain such a result is the main object of this invention. v

More particularly, my invention contemplates providing a balancing control bar and a` fulcrum therei'onwhich are capable of relative adiustment so as to unbalance the bar to the desired side and'extent, the bar being adapted to control the position' of pistons, plungers or controllers that are exposed to the p'ressure of the several control lines and thereby to maintaim the relations oi the pressure in such lines. As l such bar rocks upon its fulcrum responsive to being unbalanced, it produces a diierential movement of the pistonsor plungers which it controls and causes their relative displacement 5 with a resultant change in the pressure in the` pressure lines which they respectively control. This change will be exerted in a manner to maintain constant the relative percentages `of the applied pressure.

A further. .ieature of my invention consists in so designing the control bar and its fulcrum that its balancing point lies in the same plane withl the points ci contactabetween the bar and the elements it controls. t

My invention contemplates the interposition My invention further contemplates mounting I the fulcrum ior adjustment under screw controll relative to a gauge or scale on the control bar, thereby permitting of an accurate setting of the fulcrum according to theextent and direction of the unbalancing of the lever desired.

My invention further, where the dash control is used, contemplates applying to both the control bar and to its adjustable fulcrum, indicators which operate over exposedl scales to indicate the position of the fulcrum andthe inclination of the control bar.

My invention further comprises `the novel details of construction and arrangements of parts which in their preferred embodiments only are illustrated in the accompanying drawings and pointed out in the specification and claims, it

being understood, however, that the particular `manner, of applying power to the pressure generating pistons and the particular agencies selected to produce and control the fluid pressure, can be widely varied and applied to other uses than that shown.

As illustrated in the drawings:-

Flg. 1 is al cross-sectional view in which the housing is broken away along the line I--I of Fig. 2.

Fig. 2 is aplan view of Fig. 1 with the cover removed from lthe iluid chambers, the top hous-v ing wall broken away to Show the balancing bar and its fulcrum mechanism in plan, and one piston broken away to more fully expose its line contact with one side of the bar.

Fig. v3 is a diagrammatic layout Showing one applicationof my fluid pressure control to two independent groups of power units.

Fig. 4 is a side view. broken away to show in side elevation the control mechanism comprising the dlierential balancing bar and its adjustable iulcrum elements interposed in the transmission between the and the fluid pressure generating pistons.

Fig. 5 is av plan view of Fig. 4 with the housing and transmissionbrokn away to show one of the pressure generating p tons and the differential y actuating mechanism in plan.

Fig. 6 is a modication of my invention showing the variable leverage mechanism acting on auxiliary plungers which by relative movement determine the pressure dierence in the iiuid control lines, the housing of the control mechanism being broken away and one plunger mechanism being shown in cross-section.

Fig. is a side view of Fig. 6 with the housing broken away to show the variable leverage mechanism and part of the near control plungerin side elevation.

Fig. 8 is a fragmental front view of an indicator panel showing the control mechanism oi' Fig. 6 in front elevation. f

Fig. 9 is a diagrammatic layout showing the control of Figs. 6 to 8 applied to the front and rear brake systems of an automobile with the brake pressure controller and indicator mounted on the dash.

Similar reference numerals refer to vsimilar parts throughout the drawings. j

In the embodiment of my invention illustrated in Figs. 1 to 3, I show my improved uid pressure control mechanism operating the units Il and. II

for applying the iront. brakes by means of the` pressure line I2, and operating similar units I3 and I4 for applying the rear brakes by means of the pressure line I5, pressure being generated in these linesby the actuation of the ped'al I6. It is to be understood, however, that the brakes are typical of any other mechanisms adapted to vbe operated responsive to iiuid pressure control, and that the units Il, I'I, I3 and I4 may take the form oi.' any suitable iluid pressure motor.

I have selected as an illustrative means for generating iluid pressure, the pedal I6 which by means oi a link I1 transmits pressure to the cross head I8 to which the piston rods I8 and 2l for the pistons 2l are connected. These pistons work in separate cylinders 22 in a common housing 23. and the arrangement of parts in each cylinder being the same, the description oi one will apply to both. .Each piston 2l has a tapering recess on its outer end to receive its respective piston rod Il or 20; is circumferentially grooved to provide an oil seal; and at its inner end carries a cup washer 24 and a spring cup seat 25. A coil spring 26 engages said seat 25 and a similar seat mounted in. association with a cup washer 21`on a control plunger 28 working -incontinuation oi the same cylinder. The outer end of theplunger 28 is yoked at 28 and adapted to straddle at its re 1 spective end a balancing control bar 36, the

plunger carrying a vertical cross pin 3I in its center to provide a line bearing against the balancing bar.

In the upper portion of the housing above each cylinder I provide a separate iiuid supply chamber 32, winch chambers are separated by a partition 33 having a top equalizing port 34 and are covered overhead by a plate 35 having a filling plug 36. From each fluid chamber 32 a port 31 leads into the underlying cylinder between the cup washers 24 and 21 and is adapted tobe closed by the piston when actuated. A pressure outlet port 38 also leads from between said cup washers in position not to be closed by the piston movement and by means of a iltting 38 it delivers fluid pressure to its respective gauge line 48 or balancing bar rocks upon a transversely adjustable fulcrum 42 on a block 43 slidably seated against the rear wall of the housing and having an axial threaded bore to receive a control screw 44. This screw is mounted to rotate freely in opposite walls of the chamber 4I, being reduced at one end 45 and at the other end engaged by a plate 46 bolted to the other side of the housing and demountable to permit the insertion and removal of the screw.

The end 45 carries a tool slot 41 by means of which a screw driver can be used to turn the screw and adjust the fulcrum transversely to change the axis of the balancing control bar. As noted, this bar carries a graduated scale by means oi' which the extent of the displacement of its fulcrum on either side oi its center line is indicated. Each of the pipe lines and 40a lead to pressure gauges 48 and 48a disposed in any convenient position.

Asuming the elements assembled as described and the chambers 32 filled with a suitable fluid, upon the application of pressure to the pedal I6, both pistons 2i will be forced inwardly with equal pressure, and the iiuid will be trapped by the blanking off oi the ports 31 between the cup pistons 24 and 21 and the control plungers 28 will be subjected also to the full developed pressure winch they in turn transmit to opposite ends of the balancing bar 30.

Now if the fulcrum point be at the center of the balancing bar, the leverage thereon will be balanced, the bar will not rock about its fulcrum, and an equal pressure will be delivered through ports 38 via both pressure lines I2 and I5 vto the several -points of use in the manner that will be well understood in this art. If, however, the iulcrum point 42 be shifted out oi centrai or balanced position with reference to the control bar 38, then, when pressure is applied against the control plungers 28, the pressure applied on the longer leverage side will overcome the equal pressure ,applied on the shorter leverage side oi the bar, causing the bar to rock and allowing a relative displacement of the two plungers 23. This relativedisplacement will result in a reduced pressure on the side having the greater plunger displacement and an increased pressure on the side having the lesser plunger displacement. In other words, the short end of the oitrol bar will maintain the higher pressure and the long end the lower pressure, in the pressure lines that they respectively control. The interesting thing about this arrangementis that, regardless oi the amount oi power applied from the pedal or other source of power, the percentage oi the applied power that is effective in the two distribution lines will be a constant percentage throughout the full range of generated pressure, and by adjusting the position of the iulcrum the relative percentages allotted to the, control lines can be varied according to their respective needs.

In the embodiment oi my invention shown in Figs. 4 and 5, the elements 2i, 24, 25, 26 and 32 to 4I, are as described in connection with Figs. l and 2. 'Ihe springs 26 in this design bear against the rear ends .of the cylinders in the modied housing 50. Each piston 2| is rigidly connected to its piston rod 5I or 52 which passes freely through the end wall 54 oi its cylinder and is loosely iitted betwen the yoke arms 55 of a pedal connector 58. VThe yoke carries top and bottom plates 51 and 58 bolted thereto and the piston rods each carry an end bearing pin 59, which pins engagev the ends of the control bar 60 having ends received in bifurcations 6| formed at the outer ends of the piston rods. The balancing bar has its face engaging the fulcrum 62 countersunk so as to lie substantially in the same plane with its points of engagement with the pins 59. The fulcrum point is carried on the slide block 63 which bears against the inner end of the yoke and is controlled by a screw 44 having the parts 45, 46 and 41 as already described 10 which are mounted in the sides of the yoke 55 in a manner to permit the fulcrum. point to be shifted throughout'the requisite range of adjustment. The fulcrum blocks 43 and 63 each carry 'an indicator pin 64, which, as shown in 15 Fig. 1, extendsthrough a cover plate 65 above the equalizer chamber 4l, and as shown in Fig. 4 projects through the top cover plate 51. In each case, if desired, the pointer will be associated with a scale to indicate the relative displace- 20 ment of the fulcrum point with reference to its central or pressure `equalizng position; If it be desired to set the pressure for applying the iront brakes at 40% and the rear brakes at 60% of the pedal generated pressure, then a screw driver is applied to screw 44 at 41 and the screw turned in a direction to draw the fulcrum block 43 'toward the operator, therebysetting the fulcrum point o center and leaving the longer end of the bar 30 opposite the plunger that controls the pressure inline l2. Then an equal given pressure being on the plungers 26, the one bearing on the long end of the bar will overbalance the one bearing on the short end, causing relative movement of the plungers and thereby decreasing the pressure in the line l2 lcontrolled by the outgoing plunger and increasing the pressure in the line l5 controlled by the incoming plunger. Thus, a differential pressure is established in the lines I2 and i5 which diierential 'is responsive to difference in leverage caused by the shifting of the fulcrum point oil center, and this difference is such that throughout the range of variation in the pressure generated by the pistons 2l, the percentage of the generated pressure available for the front brakes Will'be 40% and for the rear brakes 60%. By shifting the fulcrurn point more or less this relative percentage can be varied and by shifting -the fulcrum point past center in the other diof the fulcrurn the pressure differential remains av constant throughout' the full stroke -of thebrake pedal and the resultant range ci brake applying pressure.

The operation of the arrangement shown in Figs. 4 and 5 is the same as that above described, it being desirable to bring the point of engagement between the balancing bar and its control mon plane, if very accurate control of the pressuredifferenti-al is desired. .The pins 59 have a sliding engagement with the balancing bar which permitsit to rock without putting a lateral strain on the pistons.

The springs 26, Fig. 5, will cause the pistons to move together` until they cut oi the ports 3l simultaneously.' has the pistons start their advance they displace fluid, into the chambers 32 until ports 31 are blanked. Aftervthis, the development of pressure begins' subject to the control above described. On the back stroke, the springs push the pistons out the same distance,

open ports 31 and allow iluid to ll the cylinder 7 5 and replace airy line loss.

rection the pressure diierential is reversed in.A the lines l2 and l5. For each operating position elements 59 and 62 substantially into a com-y the leads 40 and 40a extending past the gauge connections and each entering its respective control cylinder in the housing 10 through a re-4 ducer plug 12 screwed into the outer end of each end of each cylinder 13. Aspring 14 is interposed between each plug 12 and a cup washer 15 carried by an auxiliary plunger 16 which by means of the pin 3| engages the balancing bar 30 which coacts with its fulcrum 42 on the slide block 43 that is adjustable under control of the screwi44 in the manner already described. The screw 44 in this arrangement is controlled by a knurled wheel 11 and the block 43 carries on its side engaging the end wall of the housing an indicator pointer 64 which extends through a suitable slot 18 in the end wall of the housing and through the dash 1l and through a slot 10 in the indicator plate 60. This pointer coacts with a scale or gauge 2l onv the plate 80.

The balancing bar has an indicator 82 extendfing through aligning slots 63 in the housing and $4v in the plate 8,6 and. its pointercoacts with a scale 85 toindicate the angular displacement of the equalizing bar 30 while'the position of the pointer 64l indicates the off-center position of the fulcrum. v

The equalizer chamber in the housing being closed aboveand below by plates 66 and 61 which are suitably bolted to the housing, and the indicator plate 80 is held in place by screws 68 which mount the housing 10 on 4the dash panel.

In the operation of this embodiment of my invention, when pressure is applied by the pedal Il 6, the resulting pressure has access through the lines 40 and 40ct to the auxiliary plungers 16 in the housing 10 and is thereby transmitted through pins 3l to the balancing bar 30, which is permitted to rock on its fulcrum when the fulcrum is out of central position and thus establish a differential pressure as above described in the pressure lines l2-and I5.

The plug tlivpermits both chambers to be filled through oneport. Should either line break, only its respective fluid supply chamber 3 2 will be drained, the other chamber 32 4and the Huid vpressure system it supplies being Aunaffected by such break. v

The car driver can, by manipulating the screw 1,1, apply the desired percentagevof pressure on the front brakes, making this pressure as much Y lighterthan that on the back brakes as conditions throughout the full range of pressure applied at the pedal. My invention, therefore, will maintain a constant proportion ofv braking effort be- L tween the front and the rear brakes during the entireA stroke of the pedal and the percentages of pressure applied to the front and rear brakes respectively will not change due to the pedal movementor the increase in pedal pressure.

My invention is obviously not limited in its application to the number of elements i6 tov i4 controlled by the lines l2 or i5, it being understood that these elements conventionally illustrate any agency or mechanism upon which the control pressure is to exert itseiect. Inlike mannerv the pedal is typical of any source of variable power to create the pressure in the control system.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What Iclaim is:- t

1. In a fluidpressure control means, two fluid pressure generators, a separate distribution line for each generator, and means to maintain automatically va predetermined difference in pressure in said lines comprising a pressure generator and a pressure controller responsive to the pressure in each line, and a variable leverage means adapted to effect relative differential movement of said controllers.

2. In a fluid pressure control system, cylinders, pistons for said cylinders, means to actuat'e the pistons to generate fluid pressure, a separate distribution system supplied by each cylinder, and a variable leverage controller means comprising pressure regulating pistons operable on both pressure systems and automatically responsive to variations in the -pressure generated to establish in each system a predetermined percentage of such pressure.

3. In combination separate systems for the fluid pressure control of brakes, means to generate a variable pressure in said systems, and controller means to maintain in each system a predeter- .mined percentage of the generated pressure unaffected by variations thereof, said controller means comprising a balancing bar, a movable fulcrum therefor, and a fluid pressure operated i pressure control element for each system relatively and differentially movable under the control of said bar.

4. Means for controlling the distribution of the available braking effort to front and rear wheel brakes, comprising a fluid'pressure operating system for each set of brakes, a common control means actuated by the fluid pressure in both systems and acting on the fluid pressure in each system to make a fixed percentage of available braking effort effective for eachset of brakes, and means to vary the fixed percentages.

5. Means for controlling the distribution ofthe available braking effort to front and rear wheel brakes, comprising a fluid pressure operating system for each set of brakes having. a pedal actuated plunger in each system to generate the brake operating .fluid pressure, and a common control means acting on the fluid pressure generated in each system to make a fixed percentage of available braking effort effective for each set of brakes and comprising a lever of the first order, a pressure controller piston for each system` one of- 'which bears on each end of said lever, and a shiftable fulcrum f or said lever to vary the leverage and effect relative opposed movement of said controllers.

y 6. Means for controlling the distribution of the available braking effort to front and rear brakes, comprising separate fluid pressure distributionv systems for the front and rear brakes, pedal control means tending to generate an equal pressure in both systems, a controller exposed to the fluid pressure for each set of brakes, a balancing bar having. its ends operable by said controllers, and a movable fulcrum for said bar adapted to be set to vary the relative leverage effect of said controllers on said bar and to pro- .duce thereby a differential movement of said controllers.

7. A controller means according. to claim 6, in which the points of contact between the bar on the one hand and said controllers and fulcrum on the other lie substantially in a common plane.

8. A controller means according to claim 6, in which the fulcrum carries an indicator means to show its off-center relationship to the bar.

9. A controller means according to claim 6, in which the bar has an indicatormeans to show changes in the angular position of thebar responsive to variations in the available braking effort.

10. `A control means according to claim 6, in which the pressure generator and controller for each system comprise opposed pistons in com-- bination with coiled springs interposed between each pair of opposed pistons to restore parts to initial position upon release of braking pressure.

11. A control means according to claim 6, vin

supply fluid thereto and distribute fluid pres-v sure therefrom to front or rear brakes, a controller exposed to the fluid pressure for each set of brakes, a balancing bar having its ends operable by said controllers, and a movable fulcrum for said bar adapted to be set to 'vary the `relative leverage effect of said vcontrollers on said bar, the balancing bar and its shiftable fulcrum being interposed in the transmission between said pedal and pistons.

13. Means for controlling the distribution oi' the available braking effort to front and rear brakes, comprising a pair of pedal operated pistons, a cylinder for each piston with means to.

supply fluid thereto and distribute fluid pressure therefrom to front or rear brakes, a controller exposed to the fluid pressure for each set of brakes, a balancing bar having its ends operable by said controllers, and a movable fulcrum for 

